1. Field of the Invention
The present invention relates to data storage and record media each having an extremely large data storing capacity, particularly apparatus and methods for employing such media in a user data processing or other information handling environment.
2. Description of the Prior Art
Rewritable or erasable media have been used for years for recording all forms of information-bearing signals. In data processing environments, such media should exhibit low error rates for ensuring data integrity and rapid storage and recovery of data. Typically, rewritable or erasable media have been of the magnetic recording type. Such magnetic media has taken the form of magnetic tapes, magnetic disks (direct access storage devices--DASD) and magnetic drums. When such disk media are first used in a recording environment, each medium has to be initialized for recording, including formatting. Such formatting, depending upon the environment, may include an extensive surface analysis with the recording of control information in various addressable data storage areas of the record medium. Typically, in large capacity magnetic storage disks, such a control record is often called a home address (HA) record as set forth in the Bohl document (pages 73 and 74). Such initialization and surface analysis results in identification of the location of media defects. Then the locations and extents of such media defects are recorded in the home address area. This arrangement allows a recorder to skip over the identified defects. Such arrangements, improve the yield of magnetic media and, therefore, greatly reduce the cost.
Another example of magnetic disk initialization is the formatting of the so-called flexible diskettes used on today's personal computers. Such diskettes are often referred to as being "soft sectored". To enable the personal computer to record and read data on and from such diskettes, a format operation by the personal computer does a surface analysis for identifying unrecordable areas on the diskette and for recording control indicia on the diskette for enabling the recording operations.
A problem arises for a user or customer of such media when the media data storing capacity becomes extremely large, such as in the gigabyte range. Then the time required for such soft sectoring and initialization may become oppressive. Accordingly, a better solution to the present day soft sectoring and media initialization is desired.
The above referred to magnetic disk media can be overwritten without first erasing the previous contents. In some magnetic media, such as many magnetic tapes, such overwriting was usually preceded by an erasing step. In the magnetic tape situation, where erasure is first provided, the procedure of so-called "updating data records in place" is not permitted. As a result, magnetic tape was usually written from the beginning of the tape to the end of the tape in one pass for the above stated reason and other operating parameters beyond the scope of the present description.
Optical recording media has almost an order of magnitude greater data capacity for a given sized recording area than the current day magnetic recording media. Many current day optical media are hard sectored, i.e., the sector marks are molded into the media before shipment from a media factory. Such molding occupies media space which could be used for data storage. Also such media to date has been write once/read many (WORM). On the other hand, magnetooptic media is rewritable but currently requires that the previous recordings be erased before new data is recorded in any given data storing area. Therefore, to update a data record recorded on a magnetooptic medium requires a first scan of the record area for erasing the previously recorded data, a second scan over the record area to record the updated version of the data and when write or record verification is required or desired a third scan for reading the just recorded updated data. For magnetooptic disk media, a complete rotation of the disk is required between the erase scan and the write scan resulting in a relatively low performance magnetooptic recorder. While a separate erase head and a separate write head could be provided on two different actuators, the attendant cost could make magnetooptic recorders noncompetitive. Accordingly, it is desired to provide better control procedures for using magnetooptic media in information-bearing signal recorders. Such erase-before-record requirements also presently exist in the so-called phase-change optical disks wherein the recording is represented by the material phases of amorphous and crystalline states.
Optical media, including magnetooptic and phase change, are currently subject to many media defects. Since the recording density per unit area is much higher, the sensitivity of the recording to small defects becomes pronounced. Accordingly, such optical media even though being of a high quality, exhibits a high error rate because of the small areas of the media surface employed for recording information-bearing signals.
When such media are employed for use in a data processing environment, a most efficient use of the media is provided by the so-called "count key data" format as described in Bohl supra, on page 27 and pages 73-75. Another format commonly used in recording information-bearing signals is the fixed block architecture format which arbitrarily divides the disk surface into addressable areas containing a fixed number of recorded signals such as 2 K, 4 K bytes per addressable area. Such formatting requires identification of all of the fixed bytes areas. The fixed block architecture is referred to and described on pages 27-28, 82-84 and 125 and 126 of the Bohl book supra. Such fixed block architecture is often found on lower performing data processing environments, such as in the personal computer environment.
A significant difference between the CKD and the fixed block architecture is that the CKD format uses only an index mark for each of the record tracks on a disk plus a home address area and count fields as referred to above. The record size is variable such that the data records are recorded as units of contiguous signals not dissected and distributed into a group of fixed block-size sectors. Further, when recording a large number of small records in CKD, a relatively large number of control signals are associated with such small records; still all of the data storage space can be used for the data and the control records rather than leaving unrecorded areas as found in fixed block architecture. Accordingly, means are desired for effectively using the CKD format on optical disks in an efficient and low cost manner. Such efficient use may require the interactivity between a control unit and a recorder and in some circumstances, interactive operation between a host processor, a control unit and a recorder.